Which of the following mechanisms directly regulates the constriction or dilation of the afferent arteriole to control GFR?

Question

BlackTom AI · Accepted Answer

Question restatement: Which mechanism directly regulates the constriction or dilation of the afferent arteriole to control GFR?

Option 1: Tubuloglomerular feedback. This is the intrinsic renal mechanism in which the macula densa cells sense NaCl delivery in the distal tubule and adjust afferent arteriole tone to modify GFR accordingly. If NaCl delivery is high, the afferent arteriole constricts to reduce GFR; if it’s low, it dilates to raise GFR. This direct local control of the afferent arteriole is precisely what tubuloglomerular feedback describes.

Option 2: Renin-angiotensin-aldosterone system. The RAS is a systemic hormonal mechanism that primarily increases efferent arteriolar constriction via angiotensin II and can influence GFR indirectly. However, it is not the direct mechanism that governs afferent arteriole constriction in response to tubular flow; its main effect is on efferent tone and overall blood pressure regulation.

Option 3: Sympathetic nervous system. Sympathetic activation can constrict renal arterioles, including the afferent, thereby reducing GFR during stress or hypovolemia. While this does alter afferent tone, it is a neural regulatory pathway rather than the intrinsic, direct tubuloglomerular feedback mechanism that responds to tubular flow and NaCl delivery. Some texts acknowledge neural influence, but it is not the primary direct mechanism described for local control of the afferent arteriole in response to tubular signaling.

Option 4: Glomerular basement membrane. The glomerular basement membrane is part of the filtration barrier, not a mechanism regulating arteriolar tone. It determines what gets filtered, but it does not constrict or dilate the afferent arteriole to control GFR.

In summary, option 1 provides the direct, intrinsic mechanism that links tubular flow to afferent arteriolar tone and thereby regulates GFR, whereas the other options describe regulatory influences that are either indirect, neural, systemic, or structural rather than direct arteriolar regulation.

6529 SEM-2 2025 BRUCE ON-CAMPUS AND 7896 SEM-2 2025 BRUCE ON-CAMPUS Lab Exam 2 Practice Quiz (2nd)

Which of the following mechanisms directly regulates the constriction or dilation of the afferent arteriole to control GFR?

View Explanation

Log in for full answers

Similar Questions

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

Which of the following statement regarding cost is correct:

Under the assumptions used in cost-volume-profit analysis, as the activity increases:

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler